This invention relates to ducting and in particular to a fire protection system particularly suited for ducts made of fiberglass and other high temperature corrosion resistant plastic.
Ducting is widely used for exhausting gases and vapors in many industrial and commercial installations. The ducting passes through walls and other fire stops and presents a problem with fire control since flames and high temperature fluids can move through ducting causing undesirable spread of fire, smoke, fumes and the like.
A substantial amount of ducting in use is formed of metal and a wide variety of fire protection devices are available for metal ducting. Typically a temperature detector of some nature is positioned in the pipe and when the temperature in the pipe rises to a predetermined value, a damper is closed, blocking movement of flame through the pipe. A counter weighted damper may be held in the up or open position by a fusible link which when melted, permits movement of the damper.
However many ducting installations are required to handle highly corrosive vapors and the metal duct is not satisfactory. Fiberglass duct is extensively used today to meet the requirement of high temperature corrosion resistance and the damper type fire protection systems are not suitable for use therewith. One approach to the problem has been to install sprinkler heads within the fiberglass ducts, with the sprinklers controlled by temperature sensors. This is an expensive type of installation and has not been entirely satisfactory. As used herein, fiberglass is intended to include those plastic materials having high temperature corrosion resistance and used in the manufacture of ducting.
In one approach to this problem, a thermoplastic sleeve is used as a splice between two lengths of duct. When flames or high temperature fluids pass through the duct, the sleeve is softened and collapses, blocking flow through the duct and permitting entry of outside air. However this system has some disadvantages, including the fact that the integrity of the fiberglass duct is compromised and that the direct exposure of the plastic sleeve to the ambient atmosphere tends to make the softening temperature of the sleeve less certain.
It is an object of the present invention to provide a new and improved fire protection system for use with high temperature corrosion resistant ducts, which system does not utilize any metal components so that the corrosive fluid handling capabilities of the duct is not adversely affected and which does not require any breaks in the duct. A further object is to provide such a fire protection system which is simple, easy to install, and relatively inexpensive.